Suppression of backscattering-induced noise by sideband locking based on high and low modulation frequencies in ROG

Backscattering-induced noise is a dominant noise in a resonant optic gyroscope (ROG). This paper proposes a method to suppress the carrier and backscattering-induced noise with a sideband locking technique. The resonant cavity can be taken as a band-pass filter, and the carrier frequency component can be located at the stop-band while one sideband is locked to the cavity resonance. Then, the carrier will be suppressed by the cavity itself, which will reduce the interference with carrier backscattering. For the adoption of different modulation frequencies in clockwise (CW) and counter-clockwise (CCW) directions, the first-order sidebands of CW and CCW have a frequency offset to each other. Therefore, the first-order sideband backscattering can be eliminated when the sideband is locked to the cavity resonance. Also, both high and low modulation frequencies are applied to the phase modulator, which will further suppress the carrier, and the demodulation of low frequency will reduce the sensitivity to phase fluctuation noise in the system. The method has low requirements for parameter accuracy or device performance.